The odour seems
delightful to them, though dogs at least do not eat carrion.
Mr. Bartlett has observed wolves for me, and has given them carrion,
but has never seen them roll on it. I have heard it remarked,
and I believe it to be true, that the larger dogs, which are
probably descended from wolves, do not so often roll in carrion
as do smaller dogs, which are probably descended from jackals.
When a piece of brown biscuit is offered to a terrier of mine
and she is not hungry (and I have heard of similar instances),
she first tosses it about and worries it, as if it were a rat
or other prey; she then repeatedly rolls on it precisely as if it
were a piece of carrion, and at last eats it. It would appear
that an imaginary relish has to be given to the distasteful morsel;
and to effect this the dog acts in his habitual manner,
as if the biscuit was a live animal or smelt like carrion,
though he knows better than we do that this is not the case.
I have seen this same terrier act in the same manner after
killing a little bird or mouse.

Dogs scratch themselves by a rapid movement of one of their hind-feet;
and when their backs are rubbed with a stick, so strong is the habit,
that they cannot help rapidly scratching the air or the ground
in a useless and ludicrous manner. The terrier just alluded to,
when thus scratched with a stick, will sometimes show her delight
by another habitual movement, namely, by licking the air as if it
were my hand.

Horses scratch themselves by nibbling those parts of their bodies
which they can reach with their teeth; but more commonly one horse shows
another where he wants to be scratched, and they then nibble each other.
A friend whose attention I had called to the subject, observed that
when he rubbed his horse's neck, the animal protruded his head,
uncovered his teeth, and moved his jaws, exactly as if nibbling
another horse's neck, for he could never have nibbled his own neck.
If a horse is much tickled, as when curry-combed, his wish to bite
something becomes so intolerably strong, that he will clatter
his teeth together, and though not vicious, bite his groom.
At the same time from habit he closely depresses his ears,
so as to protect them from being bitten, as if he were fighting
with another horse.

A horse when eager to start on a journey makes the nearest approach
which he can to the habitual movement of progression by pawing the ground.
Now when horses in their stalls are about to be fed and are eager
for their corn, they paw the pavement or the straw. Two of my horses
thus behave when they see or hear the corn given to their neighbours.
But here we have what may almost be called a true expression, as pawing
the ground is universally recognized as a sign of eagerness.

Cats cover up their excrements of both kinds with earth;
and my grandfather[17]{sic} saw a kitten scraping ashes over
a spoonful of pure water spilt on the hearth; so that here
an habitual or instinctive action was falsely excited, not by
a previous act or by odour, but by eyesight. It is well known
that cats dislike wetting their feet, owing, it is probable,
to their having aboriginally inhabited the dry country of Egypt;
and when they wet their feet they shake them violently.
My daughter poured some water into a glass close to the head
of a kitten; and it immediately shook its feet in the usual manner;
so that here we have an habitual movement falsely excited
by an associated sound instead of by the sense of touch.

Kittens, puppies, young pigs and probably many other young animals,
alternately push with their forefeet against the mammary
glands of their mothers, to excite a freer secretion of milk,
or to make it flow. Now it is very common with young cats,
and not at all rare with old cats of the common and Persian breeds
(believed by some naturalists to be specifically extinct),
when comfortably lying on a warm shawl or other soft substance,
to pound it quietly and alternately with their fore-feet;
their toes being spread out and claws slightly protruded,
precisely as when sucking their mother.